Diaphragm pump with closed spring chamber



' Dec. 26,1967

D. TOSCHKOFF DIAPHRAGM PUMP WITH CLOSED SPRING CHAMBER Filed Nov.

INVENTOR.

ATTORNEY United States Patent 3,359,915 DIAPHRAGM PUMP WITH CLOSED SPRING CHAMBER Dimitar Toschkolf, Flint, Mich., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Nov. 26, 1965, Ser. No. 509,725 1 Claim. (Cl. 103-150) ABSTRACT OF THE DISCLOSURE A pump having an unvented spring chamber of substantially constant volume despite up and down motion of a pumping diaphragm partially defining that chamber.

Specification This invention relates to a diaphragm fuel pump and more particularly to an automotive fuel pump in which a spring chamber is unvented and substantially of constant volume and also to a sub-assembly for such a pump.

The scope of the invention is defined by the appended claims and important features of the invention will now be described in detail.

In the drawings:

FIGURE 1 shows a cross-sectional view of a fuel pump, the latter being connected to an indicator switch and warning circuit, the pump per se and the combination being in accordance with the teachings of the present invention; and

FIGURE 2 shows a cross-sectional view of a modified version of the pump with no indicator being employed.

The pump of FIGURE 1 is provided with a sheet metal structure 10 much like that of application S.N. 489,104. It includes a fuel inlet at 12 and an outlet 14 and is similarly driven as by a rocker arm 16 pivoted at 18 on a pump body 20. The arm 16 conventionally cooperates with a spring 22 to reciprocate a plunger 24 and a pumping diaphragm 26 as well as diaphragm retainer plates 28 and 30.

In providing the present invention, the body 20 is made with a spring cavity 32 which is closed to the atmosphere. A threaded boss 34, however, is made integral with the body and connects the spring cavity 32 by means of a line 36 to a pressure switch 38. When supplied with pressure this switch is adapted to close a circuit 39 which in turn may cause a lamp 41 to glow or some suitable device to make a warning sound. Such a switch is disclosed in the US. Patent 3,109,908 granted Nov. 5, 1963, in the name of B. H. Clason.

As is conventional, the lower portion of the body 20 is open at 40 to communicate with the crankcase of a supporting internal combustion engine. In case of a rupture of the pumping diaphragm 26, gasoline will enter the crankcase and damage the engine except for the presence of a seal usually provided between the diaphragm plunger and the pump body. Heretofore, vents have been located between the pumping diaphragm and oil seal as the pumping diaphragm displaces large volumes of air as it reciprocates. The vents of prior pumps are carefully designed to prevent noise and to keep dirt out. The vents, however, increase the possibility of fire and the air contacting a given pumping diaphragm tends to dry out one side of the latter. Such drying shortens the life of the pumping diaphragm.

With the present construction, a rigid member 42 is 3,359,915 Patented Dec. 26, 1967 provided to bridge the space 40. This member may be made of metal or plastic and is slidable with respect to the plunger 24 and is perforated as at 44 to vent a chamber 46 defined between the rigid member 42 and a flexible sealing diaphragm 48. An annular retainer 50 is urged downwardly by a pumping spring 52 tightly to hold the peripheries of the sealing diaphragm 48 and the rigid member 42 with respect to the body 20. The diaphragm 48 has a thickened hub 54 tightly held on the plunger 24 to move therewith. The retainer 50 aids in preventing a reversal of curvature in the diaphragm 48 as well as serving as a spring seat. The chamber 32 need not be vented as there is no change in volume as the plunger 24 reciprocates. Chamber 46, however, does change in volume and the ports or vents 44 take care' of this. With this arrangement, a large diameter spring 52 may be used which is lower in cost than a smaller diameter spring. A low spring rate improves the pump discharge rate and with no vent, there is less danger of fire and pump operation is quiet.

If the pumping diaphragm 26 should rupture, the pressure in chamber 32 would rise and the resultant closure of the switch 38 would trigger a signal at a remote area such as on a vehicle instrument panel. If this feature is not required the boss 34 could be plugged.

In FIGURE 2, a pump body 20' is disclosed and which is similar to the body 20 of FIGURE 1 except that no boss or connection to an indicator switch is provided for, i.e., its wall 21 surrounding the spring 52 is imperforate. As in FIGURE 1, there is no vent to atmosphere. A rigid member 42 with holes 44 is again used with a large diameter spring 52, a retainer 50, and a plunger 24. In this case, however, a sealing diaphragm 48 is used which has an annular trough 60 giving the diaphragm greater flexibility so that the spring chamber 62 volume may have some variation although remain substantially constant during each pump cycle.

I claim:

A pump including a pump body, a pumping diaphragm, a flexible sealing diaphragm, a rigid sealing member with a port therein, a plunger slidable in said rigid member and fixed to said diaphragms, said rigid sealing member and flexible sealing diaphragm having annular troughs therein surrounding said plunger and extending toward said pumping diaphragm so that said rigid sealing member may prevent reversal of curvature of said sealing diaphragm, a spring surrounding said plunger, an annular spring retainer forming a seat for one end of said spring, said body and diaphragms cooperating to define a closed chamber of substantially constant volume and enclosing said spring with said pump body having an imperforate wall surrounding said spring, and said sealing diaphragm and rigid member defining an annular chamber of variable volume and encompassed by said annular spring retainer.

References Cited UNITED STATES PATENTS 1,885,121 11/1932 Loweke 7418.2 2,102,797 12/1937 Helmet 92-168 2,323,950 7/1943 Wade 103-150 2,770,799 11/1956 Horn 103-150 2,873,688 2/1959 Elder 103-150 3,135,218 6/1964 Toschkoif 103-150 DONLEY J. STOCKING, Primary Examiner.

WILLIAM L. FREEH, Examiner. 

